The long-term goal of this project is to study the genetic control of morphogenesis. Our approach is to identify and characterize genes whose products have roles in morphogenetic processes occurring during the embryonic and post-embryonic development of Drosophila melanogaster. The specific processes under investigation are: (1) the transformation of the head of the embryo into the anterior end of the larva, (2) the rotation of the male genital disc during the pupal stage, and (3) the development of the sex-combs on the first pair of legs of the adult male fly. One of the genes currently being investigated is head involution defective (hid). Genetic studies involving recessive mutations of hid have revealed that its expression is initially required sometime during the first half of embryogenesis for the proper development of the anterior end of the larva. Post-embryonic hid expression is required for the rotation of the male genital disc and wing morphogenesis. Further investigation into the role of this gene will involve the use of cloned hid DNA. We have cloned 70kb of DNA in the chromosomal-region in which hid is located and are now searching within this DNA for the gene. In addition to the aforementioned work, we have recently recovered 11 mutations in X-chromosome genes which affect either the rotation of the male genital disc or disrupt the formation of the male sex-combs. We are now characterizing these mutations genetically to determine how many different genes have been mutated and the precise location of each of these genes on the X-chromosome.